Sudden cardiac arrest is a leading cause of death in developed countries in the Western World, like United States and Canada. To increase the chance for survival from cardiac arrest, important aspects are CPR (Cardio Pulmonary Resuscitation) and heart defibrillation given in the first few critical minutes after the incident. CPR is performed to ensure a sufficient flow of oxygenated blood to vital organs by external compression of the chest combined with rescue breathing. Heart defibrillation is performed to re-establish normal heart rhythm by delivery of external electric shock.
The quality of CPR is essential for survival. Chest compressions must be given with a minimum of interruptions, and be of sufficient depth and rate. Manually performed chest compressions is an extremely exhausting task, and it is practically impossible to give sufficient quality manual CPR during transportation of a patient.
Many different types of automatic chest compression devices have been developed to overcome this, based on a wide variety of technical solutions. Some devices comprise a piston which presses the patient's chest down with a given frequency and a given force. These devices comprise hydraulic/pneumatic mechanisms to provide a reciprocating movement for the piston. Other devices comprise a belt embracing the chest and a rotating motor with a spindle being engaged and disengaged.
Chest compressions given by automatic devices have the potential to be more forceful than manual compressions. There is a balance between 1) giving optimal blood flow to vital organs and 2) limiting the impact to the chest, to avoid internal injuries as a result of the external force being applied to the patient. Previously known automatic chest compression devices are designed mainly with respect to 1), and in many cases do not provide a satisfactory balance between 1) and 2).